702.py

# 702. Search in a Sorted Array of Unknown Size

# Given an integer array sorted in ascending order, write a function to search target in nums.  If target exists, then return its index, otherwise return -1. However, the array size is unknown to you. You may only access the array using an ArrayReader interface, where ArrayReader.get(k) returns the element of the array at index k (0-indexed).

# You may assume all integers in the array are less than 10000, and if you access the array out of bounds, ArrayReader.get will return 2147483647.

 

# Example 1:

# Input: array = [-1,0,3,5,9,12], target = 9
# Output: 4
# Explanation: 9 exists in nums and its index is 4
# Example 2:

# Input: array = [-1,0,3,5,9,12], target = 2
# Output: -1
# Explanation: 2 does not exist in nums so return -1
 

# Constraints:

# You may assume that all elements in the array are unique.
# The value of each element in the array will be in the range [-9999, 9999].
# The length of the array will be in the range [1, 10^4].


'''

Start with the max bound and seek if it exists in the reader.
Once logarithmically the right bound is found out - perform a simple binary search to find the solution to the problem

Time - O(logn)
Space - O(1)
'''

class Solution:
    def search(self, reader, target):
        """
        :type reader: ArrayReader
        :type target: int
        :rtype: int
        """
        left = 0
        right = sys.maxsize
        while (left<=right):
            mid = (left+right)//2
            if reader.get(mid) == 2147483647:
                right = mid -1
                continue
            if reader.get(mid) == target:
                return mid
            elif reader.get(mid) < target:
                left = mid + 1
            else:
                right = mid - 1
        return -1